Electric-current rectifier



Aug. 6, 1929. s. RUBEN 1,723,580

ELECTRIC CURRENT RECTIFIER Filed March 30, 1927 INVENTOR.

f M ATTORNEYS.

Patented Aug. 6, 1929 UNITED STATES PATENT OFFICE.

SAMUEL RUBEN, OF NEW YORK, N. Y., ASSIGNOR T RUBEN RECTIFIER CORPORATION,

' 0F ENGLEWOOD, NEW JERSEY, A CORTORATION OF DELAWARE.

ELECTRIC- CURRENT RECTIFIER.

Application filed March 30,

This invention-relates to electric current rectifiers and the like, which employ asymmetric couples of the dry surface-contact variety.

Rectifiers of this variety are known which are characterized by the use of a body of relatively electropositive material, employed as one electrode element, disposed in electri- .cal contactwith a body of relatively electronegative material employed as the other electrode element; there being an intervening film having inverse current blocking properties. Such rectifiers depend for their operation upon the resistance and current blocking characteristics of the film- WhlCh forms as the result of electrochemical action. Rectifiers of this variety are also known which do not depend for their action on the presence of such inverse current blocking film, but upon asymmetric conductivity along crystal axes. In this second. type of device an electrode element is coated with a crystalline material having crystals suf ficient in number and arrangement to pass a current of the desired magnitude the material commonly usedfor this purpose being cuprous oxide. p

The present invention relates particularly to the latter type of rectifying device, and has for its object generally to provide an improved construction and arrangement of parts, whereby the same may be readily manufactured and have a superior rectifying characteristic.

More specifically, an object is to provide an improved crystalline coating for the coated electrode elements of asymmetric couples which has relatively great mechanical strength, is not brittle, and will not chi oft.

, ther objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the features of construction, combinations of elements, and arrangement of parts, which will be exemplified in the constructions hereinafter set forth and the scope of the ap. plication of which will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference 1927. Serial No. 179,477.

should be had to the following detailed description taken in connection with the accompanying drawing, in which:

Figure 1 showsdiagrammatically a rectifying device constructed in accordance the present invention; and

'Flg. 2 shows in an enlarged cross-section an arrangement of co-operating electrode elements constructed to embody the present invention. 7

Referring now to the drawing, and particularly to Fig. 2,10 denotes an uncoated metallic electrode element against which is disposed a second coated electrode element 11. The crystalline coating for the element 11 is shown by the double hatching at 12, and is interposed between the elements 10 and 11, which, when disposed as indicated, form a. cell having asymmetric conductivity and are preferably'placed between conducting terminal plates 13, in -order that the resulting cell may be readil connected in an electrical circuit. A reitifying unit constructed to have four cells of the character shown in Fig. 2, respectively connected in the arms of a Wheat-stone bridge, is shown it in Fig. 1. Here the arrangement shown employs two groups which contain two cells each,-the groups being inverted with respect to each other and disposed adjacent to the central electrode plate 14. The end plates 15 of-the rectifying unit are conductively connected by means of the compression bolt 16, which is insulated from the respective couples in the groups and provides a common terminal. 16. This terminal, together with that provided by'the central electrode plate 14, comprise one diagonal of the VVheatstone bridge, which may be conveniently connected by means of the conductors 17 and 18 to the terminals of a direct current-consuming device (here indicated by with example, an ordinary commercial GO-cycle, 110-volt, AC=supply.

In the practice of the present invention, the electrode element may be any convenient metallic body which has preferably an clectro-positive characteristic, for' example, a disc of copper. The co-operat-ing electrode element 11 is formed to have a crystalline coating which is adapted to provide crystals which evidence a relatively- Y the passage of currents of commercial magnitude, when in contact with a smooth plate of electropositive material, such as plate 10.

The electrode element 11 is conveniently.

made as a copper disc or plate, coated with a crystalline coating cemented thereto in such a manner as to have disposed substantially uniformly over-its surface a layer of crystals imparting thereto substantially uniformly distributed asymmetric conductivity over the surface.

The crystalline coating here employed is retained upon the surface of the electrode element 11 by means of a neutral binder,

paste.

i. e., one which does not affect materially the conductivity of the coatingbyits presence. Such binder should fuse readily upon the application of heat, The borates as a class are suitable for this purpose. The method of producing the crystalline coating here employed involves the mixing together proper quantities of coating producing material and binder in a form that yields a This is applied to the surface of the electrode element, which is then heated until the binder has become properly fused.

The following is a specific example of the method where a coating ofcuprous oxide is to be produced:

A disc or plate of copper, which has been properly cleaned is coated with a a'ste containing a mixture of substantia ly equal parts of 'cupric oxide, and powdered metallic copper, to which a small quantity of lead borate is added, for example 1 part to 10 of the first mixture. The resulting mixture is ground if need be to a fine state of subdivision and madeinto a thin paste by the admixture of sufficient alcohol. This mixture is then applied to the surface of the copper disc in a substantially uniformly thin layer and afterwards-converted nto a dry crystalline coating by the application of heat. The discs thus heated, should be raised to a temperature of about 800 C. and then allowed tocool slowly, so that a. hard or stal structure of cuprous oxide remains, aving substantially uniform depthover the surface of the electrode element 11. Copper electrode discs thus n'oduced are coated substantially uniformly with an oxide layer three mills thick, which has a resistance to the passage of current in one direction of substantially one ohm, and a resistance of substantially 1,000 ohms to the passage of the inverse current, when the discs have an effective area of substantially one square inch. In order that an asymmetric cell constructed therefrom may be utilized to the best advantage, it is preferable to place in contact with the oxidecoated element, a washer of some soft metal such as lead foil, here indicated at 23. Such washer permits a uniform distribution of pressure over the contact area.

The pressure is provided by the assembly bolt 16. This pressure has no limiting characteristics other than the crushing strengths of the elements and may be any convenient pressure which insures the proper assembly of the device. This pressure, however, should be so applied as not to break or injure the crystalline structure in the layer 12.

The heating effected in the above example produces a reduction of the cupric oxide in the presence of powdered metallic co )per to cuprous oxide, so that the crystalline structure here contains cuprous oxide contained in a glass-like binder. The crystalline coating in consequence is relatively tough and mechanically stable and does not readily chip off, which it would otherwise do apparently on account of the difference in thermal expansive coefficients of the oxide coating and the copper.

In operation, current passes from the electrode element 11 to the electrode element 10, when the former is charged positively. Consequently it is seen-that in the device shown in Fi 1, when the conductor 19 has a positive p0 arity, current will pass by way of the adjacently-disposed electrode element 11 to the terminal plate 15, and thence by way of the bolt 16 and the conductor 18 to the direct current-consuming device; and thence by way of the conductor 17 to the centrally-disposed electrode plate 14; thence by way of an adjacent electrode element 11 to the conductor 20, leading to the alternatiif'g current source; and vice versa. when the conductor 20 has a plus polarity.

Since certain changes may be made in the above construction and different embodiments of the invention could be made without departing from the scope thereof, it is intended that. all matter contained in the above description or shown in the accomanying drawing shall be interpreted as bl u'strati've and not in a limitingsense.

Having described my invention, what I claim as new and desire to secure by Letters Patent, is:

1. In electric current rectifiers and the lilte, of the dry surface-contact variety, an asymmetric cell having an electrode element comprising a metallic body having a crystalline coating cemented thereto adapted to provide a distributed surface resistance having inverse current blocking properties, the cement being a fusion product of a neutral salt.

2. In electric current rectifiers and the like, of the dry surface-contact variety, an asymmetric cell having an electrode element comprising a metallic body of copper having av uniformly thick homogeneous crystalline coating containing cuprous oxide admixed With cementing medium adhering thereto.

3. In electric current rectifiers and the like, of the dry surface-contact variety, an asymmetric cell having an electrode element comprising a metallic body of copper having a crystalline coating containing cuprous oxide cemented thereto, the cement being a fusion product of a neutral salt.

4. In electric current rectifiers and the like, of the dry surface-contact variety, an asymmetric cell having an electrode element comprising a metallic body of copper having a crystalline coating containing cuprous oxide cemented thereto, the cement being a fusion product of a relatively small quantity of lead borate.

In testimony whereof I aifix mv signature,

SAMUEL RUBEN 

